I do not know about in the parks but at Kelly's landing in Celebration they had a lobster dinner for 12.95 last time I was there. Since I come from N.E. and try to eat lobster as much as I can one will NEVER do it for me so I did not order it but it was a very reasonable price for a place so far from home. Also if you are near a Boston Lobster Feast I hear the lobsters are unlimited. I know this does not really answer your question but I tried to provide some alternatives.
That's what I was wondering too. What exactly are vacation kingdom lunch vouchers? How much do they cost? Where do you get them? I have heard of the special Animal Kingdom vouchers for the counter service restaurants, but none that you could use at Rainforest Cafe.